1. Field of the Invention
The present invention relates to a position switch and a circuit breaker having the same, and particularly, to a position switch capable of precisely checking a position of a circuit breaker moving in a cradle from a remote distance as an electric signal, and a circuit breaker having the same.
2. Background of the Invention
Generally, a circuit breaker is classified into a fixed type and a withdrawable type. The fixed type circuit breaker has only a body, and is fixed to inside of a panel of a switchboard. On the contrary, the withdrawable type circuit breaker has an outer case such as a cradle for facilitation of maintenance and repair, and is configured to insert or withdraw only a breaker body thereinto or therefrom.
The withdrawable type circuit breaker (hereinafter, will be referred to as ‘circuit breaker’) is accommodated in a switchboard together with other electric devices so as to drive a power plant, a substation, an electric motor, etc.
The circuit breaker may be configured such that the breaker body thereof is electrically connected to or separated from the cradle fixed to a switchboard. According to an accommodation position of the breaker body in the cradle, a position of the circuit breaker may be categorized into a ‘TEST’ position and a ‘RUN’ position. More concretely, the ‘TEST’ position indicates a position where only an operation test for the circuit breaker can be performed as a bus bar terminal and a load terminal of the breaker body are separated from a bus bar terminal and a load terminal of the cradle. On the contrary, the ‘RUN’ position indicates a position where a voltage and a current can be supplied as the circuit breaker is connected to the terminals of the cradle.
FIG. 1 is a disassembled perspective view of a breaker body and a cradle of a circuit breaker in accordance with the conventional art, FIG. 2 is a perspective view of a carriage for moving a main circuit unit of the breaker body of FIG. 1, FIG. 3 is a perspective view of a position switch of the carriage of FIG. 2, and FIGS. 4 and 5 are side sectional views showing an operation of the position switch according to each position of the circuit breaker of FIG. 1.
As shown, the circuit breaker generally comprises a cradle 1, a breaker body 2, and a carriage 3.
The cradle 1 includes a horizontal frame unit 11 having the breaker body 2 thereon, and a vertical frame unit 12 having the bus bar terminal 13 and the load terminal 14, and coupled to the end of the horizontal frame unit 11 in a vertical direction.
An interlock plate 15 for interlocking the breaker body 2 according to each position (‘TEST’ position and ‘RUN’ position) of the breaker body 2 is installed at a front end of the horizontal frame unit 11, i.e., at the end in an insertion direction of the breaker body 2. On a side surface of the interlock plate 15, a testing switch block 16 and a running switch block 17 each configured to operate a position switch 31 to be later explained are installed with a predetermined gap therebetween in the insertion direction of the breaker body 2. The testing switch block 16 and the running switch block 17 are also installed to have a constant gap between switch bodies 35 and 36 to be later explained in a direction perpendicular to the insertion direction of the breaker body 2.
The breaker body 2 includes a current conduction unit, an insulation unit, and an extinguishing device.
The current conduction unit is implemented as contacts, and the contacts include a moveable contact of a bus bar terminal 21 and a fixed contact of a load terminal 22. The bus bar terminal 21 and the load terminal 22 are installed to face the bus bar terminal 13 and the load terminal 14 so as to have a test position by being separated from the bus bar terminal 13 and the load terminal 14 of the cradle 1, or so as to have a run position by being connected to the bus bar terminal 13 and the load terminal 14 of the cradle 1.
The insulation unit is formed of an epoxy mold or a bulk molding compound (BMC) resin.
The extinguishing device is configured to extinguish an arc generated when opening and closing contacts of a vacuum circuit breaker, and when breaking an accident current.
As shown in FIG. 2, the carriage 3 includes a mechanical mechanism for opening and closing contacts of the circuit breaker. At one side of the carriage 3, installed is a position switch 31 configured to check a position of the breaker body 2 by contacting the testing switch block 16 and the running switch block 17 of the cradle 1.
As shown in FIG. 3, the position switch 31 includes a switch housing 32, a testing switch 33 and a running switch 34, the switches arranged in a horizontal direction of the switch housing 32. The testing switch 33 and the running switch 34 include switch bodies 35 and 36, and switch levers 37 and 38 installed at lower ends of the switch bodies 35 and 36 and configured to operate the switch bodies 35 and 36 by being pressed with contacting the testing switch block 16 and the running switch block 17, respectively. The switch levers 37 and 38 are provided with rollers 37a and 38a at the ends thereof so as to slide on the testing switch block 16 and the running switch block 17.
Between the breaker body 2 and the carriage 3, further installed is an auxiliary device for normally operating the circuit breaker, e.g., a controller, an interlock device and an insertion/withdrawal device.
Unexplained reference numeral 15a denotes a test position determination recess, and 15b denotes a run position determination recess.
The operation of the conventional circuit breaker will be explained as follows.
Firstly, the carriage 3 having the breaker body 2 thereon is loaded on the cradle 1, and then the carriage 3 is pushed to a rear side of the circuit breaker. As a result, the position switch 31 coupled to the carriage 3 comes in contact with the testing switch block 16 and the running switch block 17 of the cradle 1, and transmits a current position of the breaker body 2 as an electric signal. More concretely, as shown in FIG. 4, once the testing switch lever 37 of the position switch 31 comes in contact with the testing switch block 16, the testing switch lever 37 is pressed while sliding on the testing switch block 16. This may cause the testing switch body 35 to generate a signal while being operated. Based on this generated signal, it is determined that the current position of the carriage 3, i.e., the current position of the breaker body 2 is a ‘TEST’ position. Here, the bus bar terminal 21 and the load terminal 22 of the breaker body 2 are not in a coupled state to the bus bar terminal 13 and the load terminal 14 of the cradle 1. Accordingly, the circuit breaker can perform only a testing operation without receiving power from the bus bar.
Next, once the carriage 3 moves to a rear side of the circuit breaker via the test position, the testing switch lever 37 of the cradle 1 is separated from the testing switch block 16. If the carriage 3 is pushed to be introduced into the circuit breaker in a state that the testing switch lever 37 has been separated from the testing switch block 16, as shown in FIG. 5, the running switch lever 38 of the running switch body 36 fixed to the carriage 3 comes in contact with the running switch block 17 installed at a rear side of the cradle 1. If the carriage 3 is continuously pushed, the running switch lever 38 is pressed by the running switch block 17 thus to operate the running switch body 36. As a result, it is checked that the current position of the circuit breaker 2 is a ‘RUN’ position. Once the breaker body 2 reaches the run position, the bus bar terminal 21 and the load terminal 22 of the breaker body 2 are in a coupled state to the bus bar terminal 13 and the load terminal 14 of the cradle 1. Accordingly, the circuit breaker can perform only a running operation by receiving power from the bus bar.
A withdrawing operation of the carriage 3 is performed in a reverse manner to the aforementioned inserting operation.
However, the conventional position switch of the circuit breaker has the following problems.
Firstly, the switch levers 37 and 38 are directly coupled to the switch bodies 35 and 36. Accordingly, if dimensioning of the switch blocks 16 and 17 and the switch levers 37 and 38 is inferior, a contact operation is not performed or the switch bodies 35 and 36 may be damaged. For instance, when the switch blocks 16 and 17 have a very low height, the switch levers 37 and 38 are not sufficiently lifted up in a pushing manner. This may cause a contact operation between the switch levers 37 and 38 and the switch bodies 35 and 36 not to be performed. On the contrary, when the switch blocks 16 and 17 have a very high height, the switch levers 37 and 38 are locked by the switch blocks 16 and 17 when the breaker body 2 is moving in the cradle 1 or when the breaker body 2 is turned on/off. This may cause damage of the switch bodies 35 and 36, or may cause the breaker body 2 to be lifted up. When the breaker body 2 is lifted up, the bus bar terminal 21 and the load terminal 22 of the breaker body 2 are not precisely coupled to the bus bar terminal 13 and the load terminal 14 of the cradle 1. This may cause a contact error.